diff --git a/plugins/vote/lib/ext/vote.rb b/plugins/vote/lib/ext/vote.rb
index 12f78f6..be349ca 100644
--- a/plugins/vote/lib/ext/vote.rb
+++ b/plugins/vote/lib/ext/vote.rb
@@ -2,6 +2,10 @@ require_dependency 'models/vote'
 
 class Vote
 
-  validates_uniqueness_of :voteable_id, :scope => [:voteable_type, :voter_type, :voter_id]
+  validates_uniqueness_of :voteable_id, :scope => [:voteable_type, :voter_type, :voter_id], :if => :allow_duplicated_vote?
+
+  def allow_duplicated_vote?
+    voter.present?
+  end
 
 end
diff --git a/plugins/vote/test/unit/article_test.rb b/plugins/vote/test/unit/article_test.rb
index 8962ac2..d24ae45 100644
--- a/plugins/vote/test/unit/article_test.rb
+++ b/plugins/vote/test/unit/article_test.rb
@@ -21,4 +21,12 @@ class ArticleTest < ActiveSupport::TestCase
     article.destroy
   end
 
+  should 'be able to vote in an article without a user' do
+    article = create(Article, :name => 'Test', :profile => profile, :last_changed_by => nil)
+    assert_difference 'article.votes_for', 2 do
+      Vote.create!(:voteable => article, :vote => 1)
+      Vote.create!(:voteable => article, :vote => 1)
+    end
+  end
+
 end
--
libgit2 0.21.2